Generally, representative large-scale display apparatuses include liquid crystal displays (LCDs), plasma display panels (PDPs), etc.
Unlike self-luminous type PDPs, LCDs require a separate illumination unit because there is no light emitting element equipped in such an LCD.
Illumination units for use in LCDs are classified into edge type illumination units and direct type illumination units according to positions of light sources. In an edge type illumination unit, light sources are arranged at left and right edges or upper and lower edges of an LCD panel, and a light guide plate is provided to uniformly distribute light throughout a surface of the LCD panel. Such an edge type illumination unit ensures enhanced light uniformity and enables production of an extremely thin display panel.
A direct type illumination unit is generally applied to displays of 20 inches or more. The direct type illumination unit advantageously has greater light efficiency than the edge type illumination unit by virtue of a plurality of light sources arranged below a panel. Accordingly, such a direct type illumination unit is mainly used in a large-scale display requiring high brightness.
Conventional edge type or direct type illumination units use cold cathode fluorescent lamps (CCFL) as light sources thereof.
Such illumination units, which use CCFLs, however, have several disadvantages, such as consumption of a great quantity of electric power because voltage should always be applied to the CCFLs, low color reproduction efficiency (about 70% that of a cathode ray tube (CRT)), and environmental pollution caused by use of mercury.
Currently, research is being conducted into illumination units using light emitting diodes (LEDs) as a solution to the above described problems.
In the case of illumination units using LEDs, turning on or off a part of an LED array is possible, so that it may be possible to achieve remarkable reduction in power consumption. In particular, RGB LEDs exhibit color reproduction exceeding a color reproduction range of 100% specified by the National Television System Committee (NTSC) and can provide more vivid images to consumers.